Bomb stabilizing structure



Dec. 10, 1963 J. L. KELLEY ETAL BOMB STABILIZING STRUCTURE 2 Sheets-Sheet 1 Filed May 16, 1951 INVENTORS: N L KELLEY RLES E. RUNYAN WITNESSES! 6 am 5 W444 Dec. 10, 1963 J. 1.. KELLEY ETAL 3,113,517

BOMB STABILIZING STRUCTURE Filed May 16, 1951 2 Sheets-Sheet 2 FIG. I I

WITNESSES: INVENTO JOHN L. KELLE CHARLES E. RUNYAN 520M 6 9-70.44 BY United States Patent Energy Commission Filed May 16, 1951, Ser. No. 226,617 1 Claim. (Cl. 102-3) This invention relates to improvements in stabilizing structure for bombs or the like for improving the aerodynamic performance of the bomb or other equivalent missile. The need for improvement in the way of stability has been particularly in connection with bombs dropped from relatively high altitudes and'under varying conditions producing circumstances such that means must be provided capable of providing forces to render the bomb stable over a relatively wide range of conditions.

The invention has found particular application in bombs having a low fineness ratio, i.e. length to diameter ratio of less than 5 to 1. This particular characteristic exists in atomic bombs and this invention has found very useful adaptation in this type of bomb. This particular type, that is shape of bomb, ballistically speaking introduces peculiar and diflicult stability problems. The problem becomes more difficult when the bomb is dropped from a higher altitude resulting in its terminal velocity being represented by a higher Mach number and the bomb being subjected to a wider range of atmospheric or environmental conditions during its flight. An unstable bomb tends to yaw or pitch and/ or roll, that is, oscillate and/ or rotate about its center of gravity. This pitch or yaw or wobble of the bomb, of course, detracts from its accuracy and reduces the reproducibility of trajectory in successive drops. The desire, from the standpoint of stability, is to cause the axis of the bomb to remain as close to tangent to its trajectory as possible. The flight of a fully stabilized bomb can, of course, be more accurately predicted and in dropping salvos of bombs the amount of dispersion both as to point of impact and time of fall can be minimized, or the amount of dispersion involved in successive similar drops can be minimized.

In one form of our invention the problem is met by the use of a tail structure for the bomb or the like in the form of a ring-shaped member or shroud having a particular shape in cross section involving a flap on one or both sides of the shroud at the after part thereof; i.e. the trailing edge of the shroud is thicker than the leading edge. In another form of the invention a plurality of equally spaced fins are employed having a shape, in cross section, comparableto that of the shroud described above. These particular shapes produce a component of lift which successfully stabilizes the bomb or missile to the extent that it may be said to be lift stabilized.

The primary object of the invention is to provide improved means for stabilizing a bomb or equivalent missile, particularly a bomb having a low fineness ratio.

Another object of the invention is to provide improved means for stabilizing a bomb or equivalent missile comprising a ring-shaped shroud member at the after end of the bomb, the leading edge of the member being so positioned relative to the trailing edge as to provide a predetermined angle of attack and the cross sectional shape of the member being wedge like and involving a flap on the outside thereof, at the trailing edge, that is the shape forming a broader unsymmetrical wedge by reason of the flap.

Another object is to provide a stabilizing structure as in the foregoing object wherein there is a flap both on the inside and outside of the member.

Another object of the invention is to provide means for stabilizing a bomb in flight wherein said means comprises a plurality of fins attached to the after part of the bomb, the fins having a shape which in cross section has a double wedge configuration, that is, the leading edge of the fin is a relatively narrow wedge shape and the after part of the fin is of relatively wider wedge shape in cross section.

Another object of the invention is to provide a bomb stabilizing fin as in the foregoing object wherein the narrower portion of the wedge shaped fin includes a relatively small angle and the wider portion of the wedge shape includes a somewhat larger angle.

Another object of the invention is to provide a fin as in the foregoing objects wherein the narrow wedge portion occupies a predetermined part of the fore and aft dimension of the fin.

Another object is to provide a fin as in the foregoing objects wherein the narrow wedge portion is as narrow as structural ridigity considerations will permit.

Another object is to provide a fin having a narrow lead: ing edge and a broader trailing edge and having concave sides.

Another object is to provide a fin wherein the trailing edge of the fin has a width of from 10 percent to 20 percent of the fore and aft dimension of the fin.

Further objects and numerous of the advantages of the invention will become apparent from the annexed drawings and detailed description, wherein.

FIGURE 1 is a side view of a bomb employing a circular shroud type of stabilizing device.

FIGURE 2 is an end view of the bomb of FIGURE 1.

FIGURE 3 is a view of the cross sectionalshape of the shroud of FIGURES l and 2 taken along line 33 of FIGURE 2.

FIGURE 4 is a view showing the cross sectional shape of a modified form of shroud.

FIGURE 5 is a further modified section. 1 i

FIGURE 6 is a side view of a bomb employing the fin construction of our invention.

FIGURE 7 is an end view of the bomb of FIGURE 6.

FIGURE 8 is a view showing the cross sectional shape of the fin of our invention taken on line 8-8 in FIG-, URE 6.

FIGURE 9 is a view showing a variation in cross sectional shape of fin.

FIGURE 10 is a view showing a further variation in cross sectional shape of fin.

FIGURE 11 is a view showing further variation in shape of fin.

Referring to FIGURE 1 of the drawings the bomb embodying a first form of the invention is shown at 10. The bomb has four equally spaced tail fins as shown at 11 of narrow wedge shape as shown. These fins are aligned with the the longitudinal axis of the bomb, and are attached to the tapering after end of the bomb as, shown. Supported by the fins 11 is a circular stabilizing shroud member 12. This member is of larger diameter at its leading edge as shown; it forms an air foil having a predetermined angle of attack. The cross sectional shape of the member 12 when employed without flaps is shown in FIGURE 3. FIGURE 4 shows the cross sectional shape of member 12. when a single side flap is employed. Its forward portion is of narrow wedge shape as shown. At one side of its after portion it is extended, that is, it has a flap forming a shape of wider unsymmetrical wedge configuration. The flap is on the outside of member 12. The member 12 acts as an air foil during flight of the bomb; its shape as shown in FIGURE 4 is such as to produce a component of lift which is in a direction to cause a righting moment tending to return the bomb to its desired path of flight whenever it tends to deviate from its desired trajectory.

The member 12 may have a cross section as shown in FIGURE 5 which is similar to FIGURE 4 except that the shape is symmetrical with a flap on both sides, that is both on the inside and outside.

The flap or flaps as described above have the purpose of improving the stability of the bomb particularly at higher Mach numbers resulting from high altitude drops. Success in achieving stability may be achieved using another form of our invention wherein a plurality of tail fins are utilized, the fins having a particular cross sectional shape.

Referring to FIGURE 6 of the drawings the bomb is shown at 15 and the stabilizing fins are indicated at 16. The cross sectional shape of the fins along line 88 is shown in FIGURE 8. Several of the fins may be employed and in practice four fins spaced 90 apart have been successfully used. The fins are ordinarily aligned with the longitudinal axis of the bomb and they are attached to the after portion of the body of the bomb which has a taper as shown. As may be observed the leading edge of the fin is of a narrow wedge shape and the angle included between the sides of the wedge in one particular bomb which was found to be successful was 544. As may be observed the after part of the fin is wedge shaped but the included angle is somewhat larger, this angle in the bomb just mentioned above which was found to be successful having been 2544. As will be observed the fore and aft dimension of the narrower wedge is approximately equal but slightly less than the fore and aft dimension of the wider wedge. The dimension of the fin in a fore and aft direction, that is, in the direction of the longitudinal axis of the bomb is defined as its chord.

The tail fin construction just described has been found to be very successful and particularly in the later part of the bombs flight where stability is particularly desired. The speed of the bomb, of course, increases during its flight and stability at the higher Mach number is, of course, extremely important.

The tail fin as described in the foregoing acts in the manner of an air foil and produces a component of lift which is in a direction causing a righting moment whenever the axis of the bomb deviates from a position tangent to its trajectory, that is, whenever it tends to wobble. Since it is primarily a component of lift produced by the fin which stabilizes the bomb it is said to be lift stabilized rather than drag stabilized. The stabilizing characteristics of the herein described fin construction have been found to be particularly effective at higher Mach numbers existing during the latter part of the flight of the bomb.

The cross sectional shape of the stabilizing fin might conceivably be that as shown in FIGURE 9. In this figure instead of there being a sharp change from a narrow angle to a wider wedge angle the shape may be reverse lenticular or, in other words, the sides of the fin are arcuate, that is, concave as shown in the figure. The curvature of the sides of the fin can, of course, be made to produce substantially the same characteristics as the shape of the fin in the previous embodiment. The difference, as pointed out, is essentially that in the shape of 4; FIGURE 9 there is no sharp change in the angle included between the sides of one fin portion and another.

Experimentation with and tests of various fins have demonstrated thatcertain variations in the cross sectional shape of the fin have marked advantages and adaptability for the purpose of achieving stability of the missile. It is considered that a fin shape wherein the fore and aft dimension of the narrow wedge portion is substantially one-fourth the fin chord would produce excellent results. This shape is illustrated in FIGURE 10. It has been found that making the narrow wedge portion as narrow as possible while still having the necessary structural strength is a very successful shape. Experience has demonstrated that for some adaptations, a very successful shape consists in the wider Wedge portion being only a very short after part of the fin as shown in FIGURE 11. In other words in this shape, the greater part of the fin is a narrow wedge with laterally extending flaps at the rear or trailing edge of the fin. Fin shapes wherein the width of the after end of the fin is from 10 percent to 20 percent of the chord length have also been found to possess the desired characteristics.

Actual tests of missiles equipped with fins constructed in accordance with the foregoing have demonstrated that we have provided a very effective fin construction for stabilizing missiles in flight particularly those missiles having a low fineness ratio.

The foregoing disclosure is intended to be representative of preferred forms of our invention; such variations, modifications and alterations as may be made by those skilled in the art are intended to be embraced within the scope of the claim appended hereto.

We claim:

A vehicle provided with stabilizing means for exposure to passage of an air stream comprising a plurality of fin members attached to the after portion of the vehicle and circumferentially spaced from each other each having a leading edge and trailing edge and in cross section through said leading and trailing edges a relatively narrow forward portion of progressively increasing thickness rearwardly therealong and a rearward portion of progressively increasing thickness rearwardly therealong with a wall portion at at least one side thereof disposed at a generally obtuse angle to an adjacent wall portion of said forward portion, and wherein the narrow forward portion of the fins includes an angle of substantially 6 and the rearward portion of the fins includes an angle of substantially 26.

References Cited in the file of this patent UNITED STATES PATENTS 2,694,364 Liljegren Nov. 16, 1954 FOREIGN PATENTS 47,917 France May 11, 1937 (Addition to No. 778,989) 48,076 France July 6, 1937 (Addition to No. 817,907) 375,260 Italy Sept. 29, 1939 

